The long-term objective of this project is the introduction of "smart stethoscope" technology to immediately, accurately, safely, easily and inexpensively detect blood vessel compromise using computerized analysis of vascular sounds. The specific goal of this project is to develop a device for surveillance of vascular bypass grafts, and renal hemodialysis access grafts and fistulas. The final product will not only detect the presence of stenosis but also its degree of severity. Advantages of the device include: high accuracy, non- invasiveness, low cost, ease of use, minimal training requirements, and immediate results. The Phase I effort focused on renal dialysis access grafts and fistulas, and showed high accuracy (p <.0001), in the detection of even small changes (<20%) in vessel caliber with a correlation coefficient of 0.92 compared to interventional radiology. Our Phase I data also suggested that some engineering modifications will likely enhance the device performance and lead to an even more clinically useful tool. During Phase II, we will test and implement specific engineering modifications, and fabricate prototypes for use in clinical studies of vascular bypass grafts, and renal hemodialysis grafts or fistulas. Study outcomes will include evaluations of accuracy, ease of use, training requirements, cost, and patient acceptance compared to the competing technologies of ultrasound dilution, and duplex US. The studies will take into account FDA recommendations for obtaining premarket approval, and we will seek a PMA or 510k approval from the FDA based upon study results. The potential market for our instrument is large given the number of individuals with either bypass grafts, or hemodialysis grafts or fistulas. [unreadable] [unreadable] [unreadable]